Compression piston

ABSTRACT

A compression damper of a shock absorber includes: a single adjustable fluid circuit configured for controlling a damping rate associated with multiple compression speeds of the shock absorber, wherein the single adjustable fluid circuit includes a fluid passageway through a base valve; and a positionally adjustable floating shim stack positioned at one end of the fluid passageway, the positionally adjustable floating shim stack configured for selectively blocking a flow of fluid through the fluid passageway.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of U.S. provisionalpatent application 62/185,132, filed Jun. 26, 2015 entitled “COMPRESSIONPISTON”, by Damon Gilbert et al., assigned to the assignee of thepresent application, and is incorporated herein, in its entirety, byreference.

BACKGROUND

Field of the Invention

Embodiments generally relate to a damper assembly for a vehicle. Morespecifically, the invention relates to a hydraulic circuit for use witha vehicle suspension.

Description of the Related Art

Vehicle suspension systems typically include a spring component orcomponents and a damping component or components. Typically, mechanicalsprings, like helical springs are used with some type of viscousfluid-based damping mechanism and the two are mounted functionally inparallel. In some instances, a spring may comprise pressurized gas andfeatures of the damper or spring are user-adjustable, such as byadjusting the air pressure in a gas spring. A damper may be constructedby placing a damping piston in a fluid-filled cylinder (e.g., liquidsuch as oil). As the damping piston is moved in the cylinder, fluid iscompressed and passes from one side of the piston to the other side.Often, the piston includes vents there-through which may be covered byshim stacks to provide for different operational characteristics incompression or extension.

Conventional damping assemblies include multiple fluid passageways (alsocalled fluid circuits), disposed within a piston, to account for varyingspeeds during compression, ranging from low speed compression to highspeed to lockout compression mode. The piston is disposed within acylinder with a limited sized diameter. A damping assembly's designtakes into account the weight of the shock absorber (including the oildisposed therein) balanced against the size (diameter) of the shockabsorber. Generally, a lighter shock absorber means a lighter vehiclefor the rider to use. Additionally, the larger the diameter of the shockabsorber (and the cylinders therein), the greater is the capability ofthe shock absorber to provide a damping function, and hence, enable anenhanced performance.

Typically, there are at least two separate fluid circuits to accommodateboth high speed compression and low speed compression of the shockabsorber. Thus, when an adjustment knob is turned, a high speedcompression circuit may be closed, and upon such closing, a separatecircuit for low speed compression may be opened. These multiple fluidcircuits are disposed within the piston (the piston being within theshock absorber's cylinder) and are limited in size due to the need formultiple fluid circuits for varying compression speeds.

As the foregoing illustrates, what is needed in the art are improvedtechniques for adjusting compression speeds within a shock absorber,while increasing the performance of the shock absorber and maintainingor reducing its weight.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the present technology fora dual piston system, and, together with the description, serve toexplain the principles discussed below:

FIG. 1A depicts a cross-sectional view of a monotube damper, inaccordance with an embodiment.

FIGS. 1B-1E depict cross-sectional views of a monotube damper, with theknob positioned in the low compression position, a high compressionposition, a higher compression position and a lockout position,respectively, in accordance with an embodiment.

FIG. 2 depicts an enlarged cross-sectional view of the compressiondamper of FIG. 1A, in accordance with an embodiment.

FIGS. 3A-3D depict an enlarged cross-sectional view of a portion of thecompression damper of FIG. 1A, in accordance with an embodiment.

FIG. 4 depicts an enlarged cross-sectional view of a portion of thecompression damper and knob shown in FIG. 1A, in accordance with anembodiment.

FIG. 5 depicts an enlarged cross-sectional view of a portion of the rodof FIG. 1A, in accordance with an embodiment.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to embodiments of the presenttechnology, examples of which are illustrated in the accompanyingdrawings. While the technology will be described in conjunction withvarious embodiment(s), it will be understood that they are not intendedto limit the present technology to these embodiments. On the contrary,the present technology is applicable to alternative embodiments,modifications and equivalents, which may be included within the spiritand scope of the invention as defined by the appended claims.

Furthermore, in the following description of embodiments, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present technology. However, the present technologymay be practiced without these specific details. In other instances,well known methods, procedures, and components have not been describedin detail as not to unnecessarily obscure aspects of the presentdisclosure.

Embodiments describe a novel compression piston disposed within a shockabsorber, wherein the compression piston has a single adjustable circuitthere through that, via a single control knob and a floating shim stackthat may be variably pre-loaded, controls damping for low speedcompression to high speed compression to lockout compression of thedamper within the shock absorber. Further, embodiments provide asecondary pre-loaded component to be applied against the floating shimstack. Additionally, embodiments provide an oil recirculation systemwithin the shock absorber, in which the same oil is used throughout thefork comprising the shock absorber; upon rebound, a portion of therecirculation system ingests the oil into the fluid filled chamber andfrom an area exterior to the compression damper and the fluid filledchamber, and upon compression, another portion of the recirculationsystem exhausts the oil out of the fluid filled chamber and into theexterior of the compression damper.

The following discussion will first briefly describe variousembodiments. The discussion then turns to a description of the FIGS. 1-5and embodiments shown therein.

FIG. 1A depicts a cross-sectional view of a monotube damper 100, inaccordance with an embodiment. The monotube damper 100 shown isconfigured for being disposed within a suspension fork. The monotubedamper 100 shows a rod 106 telescopically disposed within the cartridge102. The cartridge 102 is shown to include a fluid filled chamber 114,the compression damper 104 that is coupled with the knob 108 and themain piston 116 that is coupled with the rod 106. The compression damper104 includes the internal floating piston (IFP) 110 and the compressionpiston 112 (also called a base valve). The portion of the rod 106 thatis exposed to an oil bath within the shock absorber is indicated aselement 118.

FIGS. 1B-1E depict cross-sectional views of the monotube damper 100,with the needle in the low speed compression position, a high speedcompression position, a higher speed compression position, and a lockoutposition, respectively, in accordance with an embodiment.

FIG. 2 depicts an enlarged cross-sectional view of the compressiondamper 104 of FIG. 1A, in accordance with an embodiment. The compressiondamper 104 is coupled with the knob 108 having a hex shaft 238 withshaft threads 204 disposed thereon. The compression damper 104 alsoincludes a shaft 212 surrounding a needle 202 and a coil spring 228positioned around the shaft 212. As will be explained in more detailbelow, the compression damper 104 also includes at least the IFP 110, adowel pin 222, a pre-load hat 220, a shim stack 218 (also commonlycalled a valve stack in the industry) of predetermined stiffness, andthe compression piston 112. The compression piston 112 is disposedwithin and in between a first side 214 and a second side 224 of thefluid filled chamber 114, wherein the fluid is oil 216. The IFP 110separates the air chamber 232 (filled with air) from the fluid filledchamber 114. Also shown in FIG. 2 is a leak path 208. The leak path 208includes the curved recess 234 disposed in the shaft 212 and thepassageway 210 disposed in the wall of the air chamber 232.

FIGS. 3A-3D depict, in one embodiment, enlarged cross-sectional views ofa portion of the compression damper 104, and more specifically, the IFP110, the compression piston 112, and surrounding areas, in accordancewith embodiments. Further, FIGS. 3A-3D depict positions of the shimstack 218 at varying compression speeds ranging from low speedcompression to high speed compression to lockout. FIGS. 3A-3D show theIFP 110 with an outside seal 302 and inside seal 304, and a dowel pin222 lodged within the pre-load hat 220 and separating the needle 202 andshaft 212 of the compression piston 112 from the pre-load hat 220. FIGS.3A-3D also show the wave spring 312, the gap 310 between the inner edge332 of the shim stack 218 and a component of the base valve positionedclosest to the inner edge 332 such that the shim stack 218 effectively“floats” and is not clamped (pinched) into a particular position. Thisgap 310 is maintained during operation, regardless of whether the shimstack 218 is positioned in the low speed compression mode, high speedcompression mode or lockout mode. The shim stack 218 has an outer edge314 and the inner edge 332 (as previously noted). Also shown is thepiston face 318 of the compression piston 112, the fluid passageway 322disposed through the compression piston 112, a shim 328 and a spring326. Of note, also shown is the check valve 320 that enables fluid toflow from the second side 224 (see FIG. 2) of the compression piston 112to the first side 214 of the compression piston 112, but blocks the flowof fluid through the passageway 336 from the first side 214 to thesecond side 224.

In one embodiment, the knob 108 may be turned upwards of approximately220 degrees from its original position. It should be appreciated that inother embodiments, the knob 108 may be rotated more or less than 220degrees. It should be noted that in one embodiment, the knob 108 iscontinuously adjustable. Further, in one embodiment, the knob 108 hasone or more detents that correspond with different compression force(s).In one embodiment, the knob 108 is affixed to a hex shaft 238 of a screw(or other type of small bolt), wherein the hex shaft 238 is configuredfor rotatably coupling with the needle 202 (having a first end 236 and asecond end 226), such that by turning the knob 108, the needle 202 isalso turned, and is caused to move up or down within the air chamber232. In one embodiment, the hex shaft 238 has threads 204 thereon andthe needle 202 has matching threads 206 thereon at the first end 236 ofthe needle 202, such that when the knob 108 is turned, the hex shaft 238turns, and then the needle 202 turns and moves up and down along thethreads 204 of the hex shaft 238. The movement of the needle 202downwards will ultimately cause the second end 226 of the needle 202 topush against the dowel pin 222. The dowel pin 222 then pushes downwardagainst the pre-load hat 220. The pre-load hat 220 then pushes downwardagainst the shim stack 218. In general, the greater the rotation of theknob 108, the further downwards into the fluid filled chamber 114 thesecond end 226 of the needle 202 travels such that the dowel pin's 222downward movement causes the pre-load hat 220 to push the first end 324of the shim stack 218 further towards the passageway 322. In oneembodiment, the first end 324 of the shim stack 218 may be pushed, andthus moved, towards the passageway 322 by as much as 0.015″.

During operation, and with reference to FIGS. 1A-3D, when an event thatcauses compression within the monotube damper 100 occurs, the rod 106moves into the fluid filled chamber 114, pushing the oil 216 within thefluid filled chamber 114 in the direction of the knob 108 and throughthe compression piston 112 from the first side 214 of the compressionpiston 112 to the second side 224 of the compression piston 112. The oil216 then pushes against the IFP 110, causing the IFP 110 to travelupward (toward the direction of the knob 108). When an event that causesrebound within the monotube damper 100 occurs, the rod 106 moves out ofthe fluid filled chamber 114, and the oil 216 flows from the second side224 of the compression piston 112, through the compression piston 112,to the first side 214 of the compression piston 112. Further, duringrebound, the IFP 110 travels downward (toward the direction of the mainpiston 116).

According to embodiments, during compression, oil 216 flows from thefirst side 214 of the compression piston 112 to the second side 224 ofthe compression piston 112, at varying compression speeds, via a singlecircuit disposed within the compression piston 112. The quantity andspeed of the oil 216 flowing through the single circuit is controlledvia a manual rotation of the knob 108, such manual rotation ultimatelyadjusting the force with which the pre-load hat 220 pushes against theshim stack 218. The more force that the pre-load hat 220 uses to push onthe shim stack 218, the more fluid pressure is required to push the shimstack 218 open in order that the oil 216 may flow from the first side214 of the compression piston 112 to the second side 224 of thecompression piston 112 through the gap 316. Thus, the more resistance(provided by the shim stack 218) to the oil 216 flow through the gap316, the greater the compression damping that occurs in the compressiondamper 104 (and hence the shock absorber having the monotube damper 100therein). Additionally, in some embodiments and in response to the oil216 flowing through the gap 316, the fluid flow causes the shim stack218 to flex upwards enough to touch the wave spring 312, such that thewave spring 312 provides an additional, but light pre-load to the shimstack 218.

FIG. 3A depicts the shim stack 218 in a low speed compression position(“first position”). The knob 108 is set at a position such that thepre-load hat 220 is caused to be in contact with the shim stack 218, butthe pre-load hat 220 is not pushing against the shim stack 218 so thatthe shim stack 218 moves toward and/or into the passageway 322. In thisposition, in response to and during a compression event, fluid (oil)pressure is applied to the shim stack 218, and the second end 306 of theshim stack 218 (that has a predetermined stiffness) flexes upwards(shown as element 308) (in the direction of the knob 108). The oil 216will then flow through the passageway 322 and then through the gap 316,traveling from the first side 214 of the compression piston 112 to thesecond side 224 of the compression piston 112. If enough fluid pressureis applied (such as through a compression event causing a greater fluidflow rate), the shim stack 218 will flex upwards such that it meets andtouches the wave spring 312. The wave spring 312 has a predeterminedstiffness, and while it may flex upwards to a certain extent, the wavespring 312 presses against the upward flexing 308 shim stack 218 andtherefore applies a light pre-load onto the shim stack 218. This lightpre-load provides a resistance to any further flexing upward by the shimstack 218. The light pre-load applied to the shim stack 218 by the wavespring 312 also functions to maintain the relative positioning of thefloating shim stack 218 that is being held in place by the pre-load hat220.

FIG. 3B depicts the shim stack 218 flexing 340 in a second position,that is set for a speed of compression that is higher than the low speedcompression setting of the first position, shown in FIG. 3A, inaccordance with an embodiment. The knob 108 is set at a position suchthat the pre-load hat 220 is caused to be in contact with the shim stack218 and the pre-load hat 220 is pushing against the shim stack 218 sothat the shim stack 218 moves a certain distance (“distance one”) thatis greater than zero toward and/or into the passageway 322. In thisposition, in response to and during the compression event, fluidpressure is applied to the shim stack 218, and the shim stack 218 (thathas a predetermined stiffness) flexes upwards (shown as element 340) (inthe direction of the knob 108). Of note, the shim stack 218, whileflexed, appears to have a slightly concave shape (“concavity shapeone”). The oil 216 will then flow through the passageway 322 and thenthrough the gap 316, traveling from the first side 214 of thecompression piston 112 to the second side 224 of the compression piston112. If enough fluid pressure is applied (such as through a compressionevent causing enough of a fluid flow rate that overcomes the stiffnessof the shim stack 218), the shim stack 218 will flex upwards 340 suchthat it meets the wave spring 312. As described herein with respect tothe low speed compression positioning of the shim stack 218, the wavespring 312 functions to provide resistance to any further flexing upwardby the shim stack 218 and helps hold the shim stack 218 relatively inplace during such a compression event.

FIG. 3C depicts the shim stack 218 in a third position, that is set fora higher speed compression than the compression speed setting of thesecond position, shown in FIG. 3B, in accordance with an embodiment. Theknob 108 is set at a position such that the pre-load hat 220 is causedto be in contact with the shim stack 218 and the pre-load hat 220 ispushing against the shim stack 218 so that the shim stack 218 moves acertain distance (“distance two”) greater than “distance one” towardand/or into the passageway 322. In this position, in response to andduring the compression event, fluid pressure is applied to the shimstack 218, and the shim stack 218 (that has a predetermined stiffness)flexes upwards (shown as element 342) (in the direction of the knob108). Of note, the shim stack 218, while flexed, appears to have aconcave shape (“concavity shape two”) that is more concave shaped than“concavity shape one”. The oil 216 will then flow through the passageway322 and then through the gap 316, traveling from the first side 214 ofthe compression piston 112 to the second side 224 of the compressionpiston 112. If enough fluid pressure is applied (such as through acompression event causing a fluid flow rate that overcomes the stiffnessof the shim stack 218), the shim stack 218 will flex upwards such thatit meets the wave spring 312. As described herein with respect to thelow speed compression positioning of the shim stack 218, the wave spring312 functions to provide resistance to any further flexing upward by theshim stack 218 and helps hold the shim stack 218 relatively in placeduring such a compression event.

Of note, it should be appreciated that the shim stack 218 may movegreater or less distances than that of “distance one” and “distance two”and may be caused to have a greater or lesser concave shape than“concavity shape one” and “concavity shape two”.

FIG. 3D depicts, in accordance with an embodiment, the shim stack 218 ina fourth position, that is set for a lockout compression position, whichis for a higher speed compression setting than the compression speedsetting of the third position, shown in FIG. 3C. In one embodiment, toachieve the “lockout compression position” of the shim stack 218, theknob 108 is rotated to be positioned at its greatest possible rotation.Thus, if the knob 108 is rotatable to 220 degrees, then the knob 108 isturned to the rotation position of 220 degrees to achieve the lockoutcompression position for the shim stack 218. In one embodiment, the knob108 is set at a position such that the pre-load hat 220 is caused to bein contact with the shim stack 218 and the pre-load hat 220 is pushingagainst the shim stack 218 so that the shim stack 218 moves a certaindistance (“distance three”) greater than “distance two” toward and/orinto the passageway 322. In one embodiment, the “distance three” is themaximum distance that the shim stack 218 is able to be moved into thepassageway 322. In this position, in response to and during thecompression event, fluid pressure is applied to the shim stack 218, andthe shim stack 218 (that has a predetermined stiffness) does not respondto this fluid pressure with any movement such that the shim stack 218does not flex upwards any more than it has already flexed upwards (shownas element 344) (in the direction of the knob 108) due to second end 306of the shim stack 218 being held against the piston face 318. Of note,the shim stack 218, while flexed, appears to have a concave shape(“concavity shape three”) that has a greater concave shape than“concavity shape two”. The oil 216 will not be able to flow through thepassageway 322 because the force of the oil in the direction of the knob108 and against the lower surface 346 of the shim stack 218 is notenough to overcome the force of the pre-load hat 220 against the uppersurface 448 of the shim stack 218 in the direction of the main piston116 and the rod 106.

FIG. 4 depicts an enlarged cross-sectional view a portion of thecompression damper, and more particularly, the knob 108 and the firstend 236 of the needle 202, in accordance with an embodiment. Shown isthe knob 108, the hex shaft 238 (of a screw, small bolt, etc.) havingthe shaft threads 204, and the needle 202 having the needle threads 206at the first end 236. Also depicted are “needle distance one” 402,“needle distance two” 404 and “needle distance three” 406, according toone embodiment. In one embodiment, as shown in FIG. 4, the knob 108 andconsequently the needle 202 are positioned at the low speed compressionsetting such that the pre-load hat 220 is not applying any pre-load ontothe shim stack 218 other than that pre-load that is incidental to thepre-load hat 220 being in contact with the shim stack 218. In oneembodiment, a position of the pre-load hat 220 is a default positionthat occurs when the knob 108 is at zero degrees rotation (i.e., theknob 108 has not been manually rotated from a possible rotation positionof, for example, 0 to 220 degrees, and remains at 0 degrees, wherein the220 degrees represents a lockout compression speed position). The“needle distance one” 402 represents the amount of travel of the needle202 caused by the rotation of the knob 108 to a position between theminimum and the maximum knob rotation possibilities (e.g., 0 to 220degrees, etc.).

In relation to FIGS. 3A-3D, the “needle distance one” 402 corresponds tothe compression speed setting shown in FIG. 3B, when the shim stack 218moves “distance one” toward and/or into the passageway 322, creating theshim stack “concavity shape one”. The “needle distance two” 404corresponds to the compression speed setting shown in FIG. 3C, when theshim stack 218 moves “distance two” toward and/or into the passageway322, creating the shim stack “concavity shape two”. The “needle distancethree” corresponds to the compression speed setting shown in FIG. 3D,when the shim stack 218 moves “distance three” 406 toward and/or intothe passageway 322, creating the shim stack “concavity shape three”.

Thus, as is depicted in FIGS. 1A-4, the compression piston 112 has onecircuit (fluid pathway) there through. The opening of this circuit isselectively blocked with a flexible and positionally adjustable shimstack 218. The position (and hence the selective blocking of thecircuit) of the shim stack 218 is manipulated with the knob 108. Asdescribed herein, depending on the position of the shim stack 218, adesired damping rate for a particular compression speed of the shockabsorber (e.g., a range between the lowest speed compression to lockoutcompression [including high speed compression]) is accomplished.

The benefits of embodiments of the present technology are numerous. Forexample, embodiments have an adjustable single fluid circuit thatenables multiple damping rates for a range of compression speeds. Thisis in contrast to conventional technology which requires multiplecircuits to enable multiple damping rates for the same range ofcompression speeds. Thus, to accomplish the same damping functions,conventional technology requires a manufacture of more components for amultiple fluid circuit design and thus such manufacturing process ismore expensive than the manufacturing of components associated withembodiments of the present technology. Further, in one embodiment, thediameter of the fluid filled chamber 114 and the air chamber 232, andhence the compression piston 112 and the fluid passageway 322 thereinare larger than the diameter of the fluid passageways of conventionaltechnology. For example, a current piston diameter may be roughly 15.5.mm, whereas the diameter of an embodiment of the compression piston 112is 20 mm. The larger the diameter of the fluid passageway 322, the moreoil is able to pass there through at a greater rate, if need be, andthus such larger diameter increases the performance of the compressiondamper 104 during compression as compared to the narrower fluidpassageways within conventional technology. Thus, embodiments of thepresent technology are designed to be of a lower manufacturing cost andto have higher performance characteristics than those of conventionaltechnology.

Additionally and as noted herein, the wave spring 312 helps to maintainthe relative positioning of the floating shim stack 218 within thecompression damper 102. In so doing, the wave spring 312 also reducespotential noise problems by keeping the shim stacks 218, which aremoving components, from flopping around within the compression damper102 during operation.

Recirculation System

Conventional fork and damper technology provides for a damper placedinside of a fork leg of a fork. The damper includes a rod telescopicallypositioned with a cartridge. During compression and rebound, the rodmoves into and out of the cartridge, respectively. One end of the rod islocated in an oil bath of the fork leg (oil that serves to lubricateother moving components existing outside of the compression dampercomponents), while the other end of the rod is located in a fluid filleddamper. Conventionally, the oil within the oil bath is of a differenttype than that oil found within the fluid filled damper. Typically, therod must pass through a seal before any further portion of it enters thecartridge. This seal is designed to keep any oil from the oil bath thatis sticking to the shaft from entering the fluid filled chamber as theshaft passes into the fluid filled chamber. The seal scrapes off the oilfrom the rod's shaft as the rod's shaft enters the fluid filled chamber.Consequently, this scraping causes a certain amount of friction betweenthe rod's shaft and the seal as the rod's shaft moves into the fluidfilled chamber.

FIG. 5 is an enlarged cross-sectional view of a portion of the rod 106,and more particularly the main piston 116 and the seal head 526 shown inFIG. 1A, in accordance with an embodiment. Embodiments of the presenttechnology provide a system for reducing friction between the shaft 524and a sealing head 526 as the shaft 524 of the rod 106 moves into thefluid filled chamber 114 during compression and rebound. According toembodiments, the monotube damper 100 shown in FIG. 1A is placed within afork leg of a fork. A portion of the rod 106 is located within an oilbath within the fork leg (fork leg not shown).

FIG. 5 shows the main piston 116, the shaft 524 and the needle 530 ofthe rod 106, a U-Cup 514 that includes: the seal head 526 (thatfunctions to keep the fluid within the fluid filled chamber 114 fromexiting the fluid filled chamber 114); a lip 518; and a seal 520. Abushing 528 is shown disposed between the shaft 524 of the rod 106 andthe seal head 526 and functions at least to guide the shaft 524 into thefluid filled chamber 114. The main piston 116 is shown positionedbetween a first side 214 of the compression piston 112 and the chamber536. The needle 530 is shown to include a hole 532 through which the oil216 (see FIG. 2) may flow along pathway 510 from the chamber 536 to thefirst side 214 of the compression piston 112. The main piston 116 isshown to include a check valve 508 (also called the “mid-valve”) andrebound shims 502 through which fluid flows along pathway 506.

With reference now to FIGS. 1A, 2 and 5 and according to an embodiment,the following fluid flow and fluid recirculation, from the oil bath,through the main piston 116 and compression piston 112, out of the wallof the air chamber 232 and back to the oil bath, is described inconjunction with the functioning of embodiments of novel componentsdescribed herein.

As the fork leg, including the monotube damper 100, vibrates and shakesduring a vehicle's operation, the oil 216 in the oil bath moves aroundand ultimately temporarily adheres to the shaft 524 of the rod 106. Inresponse to an event causing compression of the shock absorber, theshaft 524 of the rod 106 moves into a portion 512 of the fluid filledchamber 114. The oil 216 on the shaft 524 also moves into the fluidfilled chamber 114. In response to an event causing a rebound of theshock absorber, the shaft 524 of the rod 106 moves out of the fluidfilled chamber 114, and the oil 216 that was temporarily adhering to theshaft 524 is scraped off and remains within the portion 512 of the fluidfilled chamber 114. As the main piston 116 moves downward and in adirection away from the knob 108, a first portion of the oil within theportion 512 of the fluid filled chamber 114 moves through the hole 532within the needle 530 and along the pathway 510 into the first side 214of the compression piston 112. Another portion of the oil 216 within thefluid filled chamber 114 moves along pathway 506, pushes open therebound shims 502 and moves through the resulting gap 504 into the firstside 214 of the compression piston 112. Thus, a portion of the oil 216that was in the oil bath is now inside of the fluid filled chamber 114.

As the shock absorber continues to compress and rebound, more oiltransfers over into the fluid filled chamber 114. The fluid filledchamber 114 then starts to become overfilled with the oil 216. Dependingon the amount of overfilling having occurred in the fluid filled chamber114, the vehicle may hit a bump that causes the shock absorber tocompress to the extent that the IFP 110 moves upwards along the shaft212 such that it becomes positioned within the recess 234. Since the IFP110 has an outside seal 302 and an inside seal 304, the IFP 110 movesinto the recess 234 enough that it loses its seal between the shaft 212and the inner surface of the wall of the air chamber 232. A gap betweenthe shaft 212 and the IFP 110 is created such that the oil 216 thenmoves out of the fluid filled chamber 114 and through the passageway 210along the leak path 208. The oil 216 then leaks back along the exteriorof the fluid filled chamber 114 and falls once again into the oil bath.

Thus, the combination of the compression and rebound movements of themonotube damper 100, along with the novel design of the seal head 526within a U-Cup 514 as well as the novel leak path 208 that includes therecess 234 etched into the shaft 212 and the passageway 210 enables anoil to be recirculated throughout the shock absorber. Such arecirculation system eliminates the friction occurring in conventionalsystems that function to keep two oils within a shock absorberseparated.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be implementedwithout departing from the scope of the invention, and the scope thereofis determined by the claims that follow.

What we claim is:
 1. A monotube damper of a shock absorber, saidmonotube damper comprising: a fluid filled chamber; a main pistonslidably disposed within said fluid filled chamber; a rod coupled tosaid main piston, said rod having a portion thereof exposed to an oilbath when not disposed within said fluid filled chamber; a compressiondamper disposed within said fluid filled chamber, said compressiondamper physically separated from said main piston and not connected tosaid rod, said compression damper comprising: a compression piston; aninternal floating piston; and a single adjustable fluid circuitconfigured for controlling a damping rate associated with multiplecompression speeds of said shock absorber, wherein said singleadjustable fluid circuit comprises: a fluid passageway through saidcompression piston; and a positionally adjustable floating shim stackpositioned at one end of said fluid passageway, said positionallyadjustable floating shim stack configured for selectively blocking aflow of fluid through said fluid passageway, said positionallyadjustable floating shim stack floating in an axial direction, saidpositionally adjustable floating shim stack not having an inner diameterthereof, or an outer diameter thereof, clamped into a stationaryposition, said inner diameter and said outer diameter concurrentlymovable an equal distance along said axial direction without deformationof said positionally adjustable floating shim stack; and an adjustmentknob coupled with said compression damper, wherein movement of saidadjustment knob alters a position of said positionally adjustablefloating shim stack with respect to said fluid passageway.
 2. Themonotube damper of claim 1, wherein said multiple compression speedscomprise: a low speed compression.
 3. The monotube damper of claim 1,wherein said multiple compression speeds comprise: a high speedcompression.
 4. The monotube damper of claim 1, wherein said multiplecompression speeds comprise: a lockout speed.
 5. The monotube damper ofclaim 1, wherein said positionally adjustable floating shim stackcomprises: a top surface; a bottom surface; a first end that remainsunclamped to any other component of said compression damper during acompression of said shock absorber and, upon a position adjustment ofsaid first end such that a first component of said compression damperprovides a first pre-load against said top surface at said first end,moves a distance into said fluid passageway; and a second end thatflexes upwards when said flow of fluid through said fluid passagewaypushes up against said bottom surface and overcomes a predeterminedstiffness of said positionally adjustable floating shim stack.
 6. Themonotube damper of claim 5, wherein said position adjustment isaccomplished via a manual rotation of said adjustment knob coupled withsaid positionally adjustable floating shim stack.
 7. The monotube damperof claim 5, wherein said first component comprises: a pre-load hat. 8.The monotube damper of claim 5, further comprising: a second componentproviding a second pre-load against said top surface at said second endduring an upward flexing of said second end.
 9. The monotube damper ofclaim 8, wherein said second component comprises: a wave spring.
 10. Themonotube damper of claim 8, wherein said first component comprises: apre-load hat, wherein a first portion of said pre-load hat pressesagainst said positionally adjustable floating shim stack, and a secondportion of said pre-load hat presses against said second component,thereby supporting said second pre-load being applied against said topsurface at said second end of said positionally adjustable floating shimstack during an upward flexing of said second end.
 11. The monotubedamper of claim 5, wherein said positionally adjustable floating shimstack comprises: a first position corresponding to a low speedcompression adjustment wherein said positionally adjustable floatingshim stack lies flat across said opening to said fluid passageway. 12.The monotube damper of claim 5, wherein said positionally adjustablefloating shim stack comprises: a second position corresponding to acompression speed greater than a minimum compression adjustment speed,wherein said second position comprises: a concave shape.
 13. Themonotube damper of claim 1, further comprising: a leak path configuredfor, upon compression, enabling oil to leak from said fluid filledchamber of said monotube damper to a position exterior to said fluidfilled chamber, wherein said leak path is part of a recirculation systemof said shock absorber, said leak path comprising: a recess in a shaftof said compression damper, wherein during said compression an internalfloating piston is pushed upwards along said shaft by said flow of saidoil until reaching said recess, at which point said oil leaks through agap between a surface of said recess and said internal floating piston,wherein said recess comprises: a curvature at one side configured forguiding said oil toward a wall of an air chamber; and a passageway insaid wall of said air chamber through which said oil flows.
 14. Amonotube damper comprising a recirculation system configured for usingonly one type of oil, said recirculation system comprising: a cartridgecomprising: a fluid filled chamber; a main piston slidably disposedwithin said fluid filled chamber; a rod coupled to said main piston,said rod having a portion thereof exposed to an oil bath when notdisposed within said fluid filled chamber; a compression damper disposedwithin said fluid filled chamber, said compression damper physicallyseparated from said main piston and not connected to said rod, saidcompression damper comprising: a compression piston; an internalfloating piston; and a single adjustable fluid circuit configured forcontrolling a damping rate associated with multiple compression speedsof said shock absorber, wherein said single adjustable fluid circuitcomprises: a fluid passageway through said compression piston; and apositionally adjustable floating shim stack positioned at one end ofsaid fluid passageway, said positionally adjustable floating shim stackconfigured for selectively blocking a flow of fluid through said fluidpassageway, said positionally adjustable floating shim stack floating inan axial direction, said positionally adjustable floating shim stack nothaving an inner diameter thereof, or an outer diameter thereof, clampedinto a stationary position, said inner diameter and said outer diameterconcurrently movable an equal distance along said axial directionwithout deformation of said positionally adjustable floating shim stack;and an adjustment knob coupled with said compression damper, whereinmovement of said adjustment knob alters a position of said positionallyadjustable floating shim stack with respect to said fluid passageway.15. The monotube damper of claim 14, wherein said multiple compressionspeeds comprise: a low speed compression.
 16. The monotube damper ofclaim 14, wherein said multiple compression speeds comprise: a highspeed compression.
 17. The monotube damper of claim 14, wherein saidmultiple compression speeds comprise: a lockout speed.
 18. The monotubedamper of claim 14, wherein said positionally adjustable floating shimstack comprises: a top surface; a bottom surface; a first end thatremains unclamped to any other component of said compression damperduring a compression of said shock absorber and, upon a positionadjustment of said first end such that a first component of saidcompression damper provides a first pre-load against said top surface atsaid first end, moves a distance into said fluid passageway; and asecond end that flexes upwards when said flow of fluid through saidfluid passageway pushes up against said bottom surface and overcomes apredetermined stiffness of said positionally adjustable floating shimstack.
 19. The monotube damper of claim 18, wherein said positionadjustment is accomplished via a manual rotation of said adjustment knobcoupled with said positionally adjustable floating shim stack.
 20. Themonotube damper of claim 14, further comprising: a leak path configuredfor, upon compression, enabling oil to leak from said fluid filledchamber to a position exterior to said fluid filled chamber.
 21. Themonotube damper of claim 14, wherein said recirculation system isconfigured for using only one type of oil in a fork.
 22. The monotubedamper of claim 14, wherein said recirculation system is configured forusing only one type of oil in a rear shock absorber.